

Not automatic (I think) and a bit clunky but the Strawberry music player does have a transcode feature so you could select music files and transcode them a certain way output to another folder. It’s not something I ever do but I did a quick test to a USB drive and it seems to work okay. It’s an option if you opt to use a gui to click through.
OTOH if you’re happy using the terminal and/or scripting then ffmpeg would be a better bet.
PS - Strawberry does have a panel where it lists “Devices” and maybe your phone could show up there and the transcoding would work a bit more automatically, wasn’t able to test that here.
Already using Debian on my desktop so an upgrade will happen sooner or later.